Conventional processes for making files, including the steps of forming the file teeth, hardening the file and cleaning the file after hardening are well known in the art. Such conventional processes are exemplified by Beckner et al, U.S. Pat. No. 2,897,692. In such processes the file teeth are formed by striking a file blank with a chisel-like tool at spaced intervals along the length of the blank.
Subsequent to the tooth forming step, the file conventionally is hardened by immersion in either a molten salt bath or a molten lead bath. If the lead bath is used, the file is first coated with a masking material to prevent accumulation of lead in the gullets of the teeth upon cooling. Subsequent to the hardening process it is necessary to clean or "sharpen" the file either to remove the scale and discoloration associated with salt bath hardening or to remove the masking material used in conjunction with the lead bath. Conventionally, this cleaning process has involved the use of an abrasive blasting process incorporating silica or aluminum oxide as the abrading material. Such abrasion has been considered necessary both to remove the undesired materials associated with the hardening process and also to smooth the surfaces of the file teeth to remove any roughness on the teeth caused by the tooth forming process.
In conventional file making processes it has also been considered necessary in the cleaning and finishing steps to erode a portion of the back sides of the file teeth to produce a proper cutting edge, as described in Aitken U.S. Re. No. 20,914. Accordingly, in such conventional processes it has been considered necessary to perform such steps with relatively hard abrasive material, such as silica. Blasting processes involving relatively non-abrasive materials, such as glass beads, have thus been considered unsatisfactory and undesirable.